A Hybrid electric vehicle (HEV) is environmentally friendly vehicle in which an engine and an electric motor are used for a power source, and generally, is driven by an electric motor using a battery power source until the vehicle starts and reaches a target speed, and is driven by suitably combining motor power and engine power according to an intention of the driver and a state of a battery.
A transmission mounted electric device (TMED) hybrid electric vehicle is a hybrid electric vehicle to which a TMED is applied, and an electric motor (driving motor) is attached to a transmission. That is, the electric motor is arranged between an engine clutch and a transmission.
The TMED hybrid electric vehicle is also driven by an electric motor using a battery power source until the vehicle starts and reaches a target speed, and an operation mode of the TMED hybrid electric vehicle is largely classified into a HEV mode in which an engine and an electric motor are driven together and an EV mode in which only the electric motor is driven.
FIGS. 1 and 2 are views illustrating a power transmission structure of a TMED hybrid electric vehicle according to the related art.
As illustrated in FIGS. 1 and 2, since a driving motor 3 is mounted between an engine clutch 1 and a transmission 2, speeds of an engine 4 and a driving motor 3 are synchronized when the engine clutch 1 is coupled.
However, in the TMED hybrid vehicle according to the related art, because a rear end of the engine clutch 1 and a rotor 3a of the driving motor 3 are fixed to each other, the speeds of the engine 4 and the driving motor 3 become the same when the engine clutch 1 is coupled so that the engine 4 and the driving motor 3 cannot be operated at optimum operation conditions thereof.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.